Process of making insulating material.



G. P. PETERSON.

PROCESS OF MAKING INSULATING MATERIAL.

APPLICATION FILED OCT. 20, 1909.

1,098,967, Patented June 2, 1914.

Fig.1.

Witnesses: Inventor":

/{ w CharIesFiFeterson 3 His Attorney lltl State of New I N blhhl lilb ml h lfih.

CHARLES l5. PETERSON, 03F

ESCHENECTADY, NEW YGRK, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROCESS OF MAKING INSULATING MATERIAL.

Patented June 2, this. serial in. 523,597.

To allwhom it may concern Be it known that l, Climates ll. Pnrnnson, a citizen of the United States, rosidingfat Schenectady, in the county of Schenectady, York, have invented certain new and useful improvements in the Process of Making insulating Material, of which the following is a specification.

his invention relates to the manufacture of material which is built up from adherent fragments. Material of this character is used quite extensively'in electrical arts, being built up from fragments of mica pressed 7 together with an adhesive substance.

Une of the objects of my invention is to improve the making" of. sheets by makingthem uniform.

l is liable to be irregular v rial adjacent ()ne of the diiliculties with mica sheets made up of fragments is that the material in density. in the manufacture of these shwts the fragments are pressed together between iron. plates and the overlapping fragments cause some parts of the sheet to be hard and others soft. The plates of course press upon the high spots and compress the sheet at these points.

llhis is particularly troublesome with mica,

sheets used in commutators. When the commutator is turned off, it is often found that the copper is carried over the edges at the places where the mica is porous, instead of there being a clean line of division, as would be the case if the mica were uniform. In order to malre the mica uniform, it is neces sary to millofl the sheets of mice on'both sides and great waste of material is entailed.

.ln carrying out my invention, 1 overcome this difliculty by applying a yielding mate- W the fragments so as to 'distribute the pressure. l have found that in compressing mica a layer of yielding materiahsuch, for instance, as asbestos, serves the purpose. By employing a pad of this material the pressure is distributed throughout the sheet which is to be formed and a product of uniform density is obtained. l have found that an asbestos pad is particularly well adapted, since it furnishes the desired yieldingproperties, and at the sfime time willwithstand the temperature which is employed in the baking of the sheets.

lfn the accompanying drawing illustrat' ing my invention, Figure 1 shows mica heets with an asbestos pad between them n a press; Fig. 2 representsthe sheets and asbestos pad as they come out of the press; Fig. 3 is a sheet of mica before it is milled oil",- Fig. 4 represents a-sheet after it is milled oil; Figs. 5 and (3 show the mica in the slots of the commut ator.

Referring to the drawings, and. '11 represent iron plates used in the pressing of the mica sheets. 'lhese plates may be pressed together in any desired manner, this feature of the process forming no part of my in vention. The plates are perforated, as shown, for the purpose of carrying the steam coils for heating the sheets built up of mica fragments in the well lrnown manner, are placed between the plates of the press with the asbestos pad 13' between them. 'lhin sheets of metal 13, as for instance, sheet iron or tin, are placed between the mica sheets and the plates of the press to prevent the mica fron'i plates, and thin sheets of impregnated paper 141- are laid between the asbestos pad and the mica for similar reason. 'l l hen pressure is applied to the plates and the sheets are baked, the .sheets will be found to be ilat andeven on next to the asbestos the even. The sheet itself, form density. This sheet, which is shown in Fig. 3, is milled off on one side only, 1 0., the uneven side, so as to reduce the sheet to the form shown in Fig. s. I

In Figs. 5 andt l have shown the difference between the use of. sheets of mice surface is very un which are of uniform density and sheets which are not. in Fig. 5 a clean line is formed between the mica and the bars 15 of the commutator, while in Fig. 6 the copper of the bar is carried over at the soft spots of the mica l6.

lit will be seen that l. have provided means whereby a uniform sheet of mica may be obtained in a very simple manner.

Various modifications of my invention will suggest themselves to those skilled in the art, and it should be understood that I do not limit my invention to the particular means and materials set forth therein except in so far as they are limited by the scope of the claims annexed hereto. 7

What I claim as new and desire to secure by Letters Patent of the United States, is-

l The ing however, is of uni process of forming mica insulat 1 material whlch consists in spreading 1 a lit;

to bake them. The mica sheets 12, which are lti adhering to the one side, whereas on the side fragments over an extended area to form a sheet, ressing the sheets between rigid plates with a compressible material adjacent the mica to give the sheet a uniform density and make the face of the sheet adjacent the yielding material uneven and then planing off the uneven surface.

. 2. The process of formingmica insulating material which consists in spreading fragments of mica provided with adhesive over an extended areatc form a sheet, pressof mica providedwith adhesive ing the sheets between rigid plates with yielding. material between the sheets to give the sheet a uniform density and make the 15 faces of the sheets which are adjacent the yielding'material uneven and then planing of? the uneven surfaces.

In witness whereof, I have hereunto set my hand thl CS 19th day of October, 1909.

HARLES F. PETERSON. Witnesses:

BENJAMIN B. HULL, HELEN Onronn. 

